Wondering why your phone keeps dying after a session or two of Angry Birds? One study says it's because you're too cheap to pay.

According to scientists at Purdue University who examined apps on Windows and Android-based phones, free applications only require about 10-30% of the energy they actually use. On the flip side, the scientists say that a whopping 65-75% of that energy goes toward powering third-party advertisements—the ones that keep those apps free. Buying the premium versions of games like Angry Birds could help alleviate this problem.